I thought about a neat feature: being able to force downpicking (like you can currently do) but add an adjustable time threshold for automatic alternate picking. So the guitar would only do downpicking above the threshold (for example 300 ms) and switch to alternate picking if the repeating notes are played faster than that.

The threshold could be controlled by MIDI CC so you can adjust it for different parts.

Actually, we are already using this strategy, except that the time threshold is not exposed to user. In future updates, we will expose it so that you can modify at which speed the down-picking will become up-down picking.